Conventionally, ethylene-propylene-diene ternary copolymer (EPDM) rubber and various types of rubber products used as automobile weather-strips are coated with a coating agent comprised of a polyorganosiloxane composition to provide their surfaces with non tackness, water repellency, abrasion resistance and lubricating properties.
Such a coating agent is known to be, for example, a composition which contains polydiorganosiloxane having hydroxyl groups at the terminal ends and polyorganosiloxane having hydrogen atoms bonded to silicon atoms and/or organoalkoxysilane and a curing catalyst.
But, such a coating agent composition generally contains an organic solvent and has safety and hygienic problems, handling problems resulting from flammability, and a problem of a large averse effect on natural environments. Therefore, a water-based emulsion type coating agent not containing an organic solvent is under development in these years.
But, if a coating agent of a type diluted with an organic solvent is directly applied to a water-based type, a coating film cannot be provided with satisfactory durability and adhesiveness (adhesion). And, there is also a problem that it is hard to provide a water-based type because a silane component reacts with water.
Meanwhile, as an emulsion type silicone (polyorganosiloxane) based coating agent, a composition containing various types of siloxane compounds is proposed (e.g., Patent Document 1).
But, this coating agent does not provide satisfactory adhesiveness and abrasion resistance of the coating film, and particularly does not provide a non foamed rubber material or a substantially non foamed rubber material with the coating film having satisfactory adhesiveness and film strength. There are also problems that the storage stability of the emulsion and the usable life after blending individual components are not satisfactory.
To improve the adhesiveness and abrasion resistance of the coating film, there is proposed a coating agent including a dealcoholic condensation type silicone-based emulsion mixed with chlorinated polyolefine having a maleic anhydride group (e.g., Patent Document 2).
In the coating agent described in Patent Document 2, however, the main component silicone is a dealcoholic condensation type silicone, and the adhesiveness and abrasion resistance of the coating film are not satisfactory.
Besides, there is also proposed a coating agent, which is a dehydrogenation condensation type silicone emulsion mixed with a particular adhesion improving component (such as an amino silane compound, an epoxy silane compound or carboxylic acid) (e.g., Patent Document 3).
But, the above coating agent is not satisfactory in terms of a uniform applying property, non tackness, water repellency, lubricating properties and adhesiveness with the substrate and demanded for further improvement.
Besides, a dealcoholic condensation type coating agent, which contains organotrialkoxysilane as a crosslinking component, and an amide group, a carboxyl group-containing organotrialkoxysilane and epoxy group containing trialkoxysilane as adhesiveness improving components, is proposed in these years (e.g., Patent Document 4).
But, this coating agent is also not satisfactory in the adhesiveness and abrasion resistance of the coating film, and a mixing method and a usable life after mixing have problems because silane having a hydrolysis property in the presence of a catalyst is mixed.
Furthermore, the coating agent is demanded in these years that, when a coated mold part in a wet state is rubbed against glass or the like, frictional sound, so-called creaking sound, is not produced or the coated surface is not damaged because of rubbing with the coated metal surface.
Patent Document 1: JP-A HEI 8-245882
Patent Document 2: JP-A 2001-207106
Patent Document 3: JP-A 2002-188057
Patent Document 4: JP-A 2003-155411